This may get a little dirty, so if you're up for it let's go! :D
I want a fun debate.

I believe that breast size has been, is, and will always be important. And not in a derogatory sense at all. Not that I have huge boobs, and not that I'm shallow in ANY way. I'm not bisexual or a lesbian. Bigger boobs are just more favorable in every aspect. Not huge balloons. But a proportional, healthy rack is completely desirable for both men and women.

My opponent assumes that big breasts are better than the average and the smaller variety of breasts.

Definition:
Since my opponent did not define better, it shall be defined as follows:
of superior quality or excellence.

"I believe that breast size has been, is, and will always be important"

While this may very well be true, big boobs may not always be the size of importance. A man who prefers breasts of the smaller variety will find it more important that a woman has smaller breasts. Such a man cannot with an honest tongue say that large breasts are either more important or better than smaller breasts.

"Bigger boobs are just more favorable in every aspect."

To whom are they more favorable in every aspect? You cannot take a subjective matter and objectify it. Neither large breasts nor small breasts are "better" in any objective sense. When a woman is trying to squeeze her body through a very narrow space, it would most certainly be better for her have smaller breasts, in which case big breast are not better in every aspect. Big breasts are not better for a person who prefers smaller breasts.

"But a proportional, healthy rack is completely desirable for both men and women."

Of course breasts need not be large in order to be healthy and proportional. And, to the contrary, Large breasts sag quicker, where as smaller breasts tend to keep their form and shape much longer and generally look better, more in proportion with the body. There is also a certain pain with lack of variety in bra types and more obstructive and uncomfortable exercising.

Is it true that men prefer big breasts? This psychology abstract in which men were polled seems to suggest that men prefer women with medium size breasts: http://www3.interscience.wiley.com...)